This invention relates to radiopharmaceutical compositions containing gallium-68 and to a generator for preparing free ionic gallium-68.
Radiochemistry presently is utilized in biological research and medical diagnosis. Certain radioactive preparations, when introduced into a biological system, will localize in specific organs, tissues or skeletal material. With radiation detecting devices such as a gamma camera or a high pressure, multiwire proportional camera, the target areas are visualized and the functioning of certain organs such as the heart, the kidney or the liver then can be monitored to diagnose a particular disease or structural defect in the biological system. Presently, the technique of tomographic reconstruction is used to obtain three-dimensional images of specific organs. These images are obtained either by utilizing an x-ray source or by administering a composition containing a photon-emitting isotope. The use of a positron-emitting isotope is preferred over the use of single photons because lower activities can be used. In addition, the use of single photons requires a collimator to obtain the desired images. The use of a positron-emitting isotope does not require the use of a collimator since they emit 2 gamma particles in directions 180.degree. from each other rather than in random directions.
Presently, the preferred positron-emitting isotopes for use in radiopharmaceutical preparations are oxygen-15, carbon-11, nitrogen-13 and fluorine-18. Unfortunately, all of these positron-emitting isotopes have a short half-life of less than 2 hours. Because of these short half-lives, it is necessary to have an on-site cyclotron producing these isotopes. Since a cyclotron is an expensive apparatus, it would be desirable to provide a positron-emitting isotope that would be available without the need for an on-site cyclotron and which can be safely administered to humans.
It has been known that it would be desirable to obtain free gallium-68, a positron-emitting isotope, in order to provide three-dimensional images. However, prior to this invention, no practical means for obtaining gallium-68 has been available. Presently, gallium-68 is available bound with ethylenediamine tetraacetic acid (EDTA). The problem with this compound is that it is cumbersome to isolate gallium-68 from the EDTA complexant so that the gallium-68 can be bound to other molecules for diagnostic use.